Early years
Iommi picked up the guitar as a teenager, after being inspired by the likes of Hank Marvin and The Shadows. In an industrial accident at the age of 15 on his last day of work in a sheet metal factory, he lost the tips of the middle and ring fingers of his right hand - which, being left-handed, he uses to fret the strings of a guitar. At first he thought his days of playing guitar were over. However, his boss, who knew of his "night job" as a pub band guitar player, paid him a visit during his recovery. During the visit, his boss encouraged him to reconsider. He played a Django Reinhardt record which inspired Tony to pick up the guitar again (Reinhardt lost mobility in the third and fourth fingers of his fretting hand in a fire). After trying to learn to play right-handed, he instead strung his guitars with extra-light strings (which he created himself by intertwining banjo strings) and wore plastic covers that were made from bottle caps over those two fingers (which he covered with leather, so he could grip the strings properly). His accident also had an impact on the Black Sabbath sound: after some time Tony detuned his guitar from E to C# (1 and 1/2 steps down) in order to ease the tension on his fingers, making Sabbath one of the first bands to detune. This idea is now a mainstay of heavy metal music. Black Sabbath bassist Geezer Butler also tuned his instrument down to match Iommi's.

Pre-Black Sabbath
Iommi has played in several blues/rock bands, the earliest of which being The Rockin' Chevrolets between 1964 and 1965. The band had regular bookings and when they were offered work in Germany, Iommi decided to leave his factory job to take up the opportunity. It was during his last shift in the sheet metal factory that Iommi lost the tips of his middle and ring fingers in the aforementioned incident.

Between 1966 and 1967 Iommi played in a band named The Rest. This was the first time Iommi played with old school friend and future Black Sabbath drummer Bill Ward.

From January of 1968 till July 1968, Iommi was guitarist in Mythology with Ward joining a month later in February. In May 1968, police raided the group's practice flat and found cannabis resin which resulted in a £15 fine and a two-year conditional discharge for Iommi, Ward and the other band members - Smith and Marshall. With no money and low morale, Mythology split up after a gig in Siloth on 13th July, 1968.

In August 1968, at the same time as the break up of Mythology, a band called Rare Breed also broke up. Rare Breed vocalist John "Ozzy" Osbourne and rhythm guitarist Terry "Geezer" Butler joined with Iommi and Ward from Mythology and also slide guitarist Jimmy Phillips and saxophonist Alan "Aker" Clarke. The six-piece band, now with Butler as bassist, were named the Polka Tulk Blues Band. After just two gigs - the last of which being at the Banklands Youth Club in Workington - Phillips and Clarke were dismissed from the band, whose name was shortened to simply Polka Tulk after this.

Iommi, Butler, Ward and Osbourne renamed their band in September 1968 to Earth. They carried on under this moniker until August 1969. Iommi briefly left in this period to play in Jethro Tull. However after only one performance (an appearance on "The Rolling Stones' Rock'n'Roll Circus" in which the band mimed to "A Song For Jeffrey", whilst Ian Anderson sang live), Iommi was back with Earth once more.

Black Sabbath
In August 1969 - after confusion with another group named Earth that had some minor success in England - the group renamed themselves to Black Sabbath.

Tony Iommi says about his working-relation with Jethro Tull vocalist Ian Anderson, which may have contributed to the success of Black Sabbath:

I learned quite a lot from him, I must say. I learned that you have got to work at it. You have to rehearse. When I came back and I got the band (Black Sabbath) back together, I made sure that everybody was up early in the morning and rehearsing. I used to go and pick them up. I was the only one at the time that could drive. I used to have to drive the bloody van and get them up at quarter of nine every morning; which was, believe me, early for us then. I said to them, "This is how we have got to do it because this is how Jethro Tull did it." They had a schedule and they knew that they were going to work from this time till that time. I tried that with our band and we got into doing it. It worked. Instead of just strolling in at any hour, it made it more like we were saying, "Let's do it!"

It may be argued that Tony Iommi was a pioneer of heavy metal riffing due to his guitar playing on now famous tracks such as "Paranoid", "War Pigs", "Iron Man", and "Into The Void". He combined blues-like guitar solos and dark, minor-key riffing with a revolutionary high-gain, heavily distorted tone with his use of a treble-boosting effect-pedal and a Gibson SG. The innovative detuning of his guitar to C#, an idea first employed on 1971's Master Of Reality album, also helped to characterise his distinctive sound.

By the mid 1970s, incessant drug usage, managerial problems and constant touring had taken its toll on the band, and Ozzy Osbourne was eventually fired in 1979. Osbourne was replaced with Ronnie James Dio, the vocalist for Rainbow, a band formed by former Deep Purple guitarist Ritchie Blackmore. With Dio, Black Sabbath produced Heaven and Hell before drummer Bill Ward was replaced by Vinny Appice. With this lineup they produced The Mob Rules, leaving Iommi and Geezer Butler the only original members.

During the 80s and 90s, Iommi rebuilt the band with many lineup changes, including vocalists Ronnie James Dio, Ian Gillan (formerly of Deep Purple), Glenn Hughes and Tony Martin, as well as Ray Gillen and Rob Halford - Judas Priest singer - as guest vocalist for just two gigs after Ronnie James Dio refused to perform at Ozzy's 'farewell' at Costa Mesa in 1992. Halford also sang at one of the dates on the 2004 Ozzfest tour, when Ozzy couldn´t perform due to bronchitis.

In 1992, Iommi appeared at the Freddie Mercury Tribute Concert, playing four songs with the remaining members of Queen and other guest artists.

The original Black Sabbath reunited as a touring band in 1997 (although Bill Ward was not present for the first two reunion tours, the second being due to a heart attack. Ward was replaced by Vinny Appice on this tour).

After Ian Gillan left in 1984, Iommi recorded his first solo album, entitled Seventh Star. The album featured Glenn Hughes (formerly of Deep Purple) on vocals, but due to label pressures, it was billed as a release by "Black Sabbath featuring Tony Iommi". In 2000, he finally released his first proper solo album, titled simply Iommi. Iommi featured several guest vocalists, including Henry Rollins, Serj Tankian, Dave Grohl, Billy Corgan, Phil Anselmo, and Ozzy Osbourne. In late 2004, Tony's second solo album was released, entitled The 1996 DEP Sessions. This album was originally recorded in 1996, but was never officially released. However, a copy with a drum track by Dave Holland (many fans agree that it was right to remove Holland from the album because of his current personal stature and also because the drum track he recorded was considered inferior) was available as a bootleg called Eighth Star. The vocalist on this album was again Glenn Hughes. After he released The 1996 DEP Sessions, Tony later released his third solo album, Fused on July 12, 2005, also with Glenn Hughes on vocals, bass and Kenny Aronoff on drums. In October 2006 it was confirmed that Iommi would tour with Bill Ward, Geezer Butler and Ronnie James Dio again though not as Black Sabbath but under the moniker 'Heaven and Hell' (Ward later opted out of the tour, to be replaced by Vinny Appice).